While local authorities have arrested dozens of alleged militants since 2004, when a key Madrid train station was attacked, Spanish media reported these were the first caught with explosives, meaning they had become an operational cell.

The three suspects -- two from ex-Soviet republics and a Turk -- had timers and enough explosives to blow up a bus, Diaz said in a press conference in Madrid. Police believe at least two of those arrested had practiced flying small "ultralight" airplanes or using small drones, Diaz said.

The suspects were arrested in Cadiz and Ciudad Real, two of them on a bus en route to France.

Spanish police told El Paiz that explosive materials found in the home of the Turk was strong enough to "completely destroy a bus".

At least one of the suspects was trained at a terrorist camp in Pakistan, according tp Spanish media. The organization had apparently been seeking out Spanish-speaking "lone wolves" in Saudi Arabia, according to El Pais.

Someone said: "there will be an explosion in their Jihanuseses, just not the kind they were expecting ;-)"